<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
<script>
    let num=10;
    console.log(num)
    function test1(){
        console.log(num)
    }
    test1()
    function test2(){
        let num=100;
        console.log(num)
    }
    test2();
    function test3(){
       // let num=20
       function test4() {
           // let num=40
            console.log(num)

        }
        test4();
    }
    console.log("-=====================")
    test3();
</script>
</html>